Deptt. of Electronics and Communication Engineering, Amity School of Engineering and Technology, Noida, India Email: 1bsingh.tech@gmail.com 2,3 Malaviya National Institute of Technology, Jaipur, India Email: 2san@mnit.ac.in, 3tarun.varma.jaipur@gmail.com controlled shift register is designed at the circuit level and integrated into the ACS module. A. Structure of Viterbi Decoder The four functional blocks of VD in term of implementation, including branch metric unit (BMU), add-compare-select unit (ACSU), feedback unit (FBU) and survivor memory unit (SMU).

Abstract—In 2G mobile terminals, the VD consumes approximately one third of the power consumption of a baseband mobile transceiver. Thus, in 3G mobile systems, it is essential to reduce the power consumption of the VD. In this report the register exchange (RE) method, adopting a pointer concept, is used to implement the survivor memory unit (SMU) of the VD. For the implementation part, hardware implementation of MLVD through Synopsys Design Compiler Synthesis is done. For synthesis UMC-180nm Library is used. Index Terms— Viterbi Decoder, SMU, ACSU, RE, MLVD I. INTRODUCTION The register exchange (RE) method, adopting a pointer concept, is used to implement the survivor memory unit (SMU) of the VD. The method entails assigning a pointer to each register or memory location. The contents of the pointer, which points to one register, is altered to point to a second register, instead of copying the contents of the first register to the second. When the pointer concept is applied to the RE's SMU implementation[2], there is no need to copy the contents of the SMU and rewrite them, but one row of memory is still needed for each state of the VD. Thus, the VDs in CDMA systems require only 256 rows of memory, hence reducing the VD's power consumption. Also, if the initial state of the convolutional encoder is known, the entire SMU is reduced to only one row. Because the decoded data is generated in the required order, even this row of memory is dispensable. The zero-memory architecture is called the MemoryLess Viterbi Decoder (MLVD)[6], and reduce power consumption. Another problem of the VD, which is addressed in this report, is the Add Compare Select Unit (ACSU) which is composed of 128 butterfly ACS modules. The ACSU's high parallelism has been previously solved by using a bit serial implementation. The 8-bit First Input First Output (FIFO) register, needed for the storage of each path metric (PM), is at the heart of the single bit serial ACS butterfly module. A new, simply

Fig.1 Functional Block of VD The BMU calculates branch metric of each branch according to maximum likelihood of the received data. The ACSU makes the sum of branch and path metrics, then compares and selects the survivor path metric and the decision bit. The FBU stores the survivor path metric for ACSU to be used in the next cycle. The SMU produces the decoded data based on the decision bit and the survivor path metric. The SMU marked by boldfaced letters in Fig. 1 significantly influences latency, power and chip area in a VD. B. Viterbi Decoding Algorithms In 1967, Viterbi developed the Viterbi Algorithm (VA) as a method to decode convolutional codes [1]. The VA uses the trellis diagram to decode an input sequence, as demonstrated in Figure 2. The VA[4], which uses a hard decision format, is exhibited in Fig.2. A node is assigned to each state for each time stage.The transition between two states is represented by a branch, which is assigned a weight, referred to as a branch metric (BM). The BM is a measure of the likelihood of the transition, given the noisy observations. The BMs that are accumulated along a path form a path metric (PM). For the two...

YOU MAY ALSO FIND THESE DOCUMENTS HELPFUL

...Keywords: tutorial, QPSK, modulation, modulator, demodulator, demodulation
May 01, 2002
APPLICATION NOTE 686
QPSKmodulation demystified
Abstract: Readers are presented with step-by-step derivations showing the operation of QPSKmodulation and demodulation. The transition from analog communication to digital has advanced the use of QPSK. Euler's relation is used to assist analysis of...

...
Kirk Samuda
Institute of Advanced Technology
Devry University
September 2005
Advanced Telecommunication
To fully understand the advantages of the various modulation techniques of analog
signals, I think it’s important to understand the very basic premise on which modulation
exist. Allow me the privilege of starting with the basic function of any communication
system, which is transmitting information from one point to...

...TRANSISTOR
24
7.
LED
27
8.
CONCLUSION
37
ABSTRACT:
The objective of our project is to design the frequency modulator and demodulator with the help of IC566 and IC565 and thus obtain the modulation of the carrier wave with respect to frequency of message signal. Frequency modulation is defined as the process of changing the frequency of the high frequency carrier signal with respect to low frequency modulating (message) signal which typically...

...QAM and QPSK:
Aim:
Review of Quadrature Amplitude Modulator (QAM) in digital communication system, generation of Quadrature Phase Shift Keyed (QPSK or 4-PSK) signal and demodulation.
Introduction:
The QAM principle: The QAM modulator is of the type shown in Figure 1 below. The two paths to the adder are typically referred to as the ‘I’ (inphase), and ‘Q’ (quadrature), arms.
Not shown in Figure 1 is any bandlimiting. In a practical situation this would be...

...Amplitude modulation or AM as it is often called, is a form of modulation used for radio transmissions for broadcasting and two way radio communication applications. Although one of the earliest used forms of modulation it is still in widespread use today.
The first amplitude modulated signal was transmitted in 1901 by a Canadian engineer named Reginald Fessenden. He took a continuous spark transmission and placed a carbon microphone in the antenna...

...(m2/2) ]
= 500W [ 1 + (0.92/2) ] = 702.5W
4. An intelligence signal is amplified by a 70% efficient amplifier
before being combined with a 10kW carrier to generate the AM signal.
If it is desired to operate at 100% modulation, what is the dc input
power to the final intelligence amplifier?
Solution: The efficiency of an amplifier is the ratio of AC output
power to DC input power. To fully modulate a 10kW carrier requires 5kW
of...